Q.35 Which of the following statement(s) is/are correct for the following compound?
(A) It can have a maximum of four stereoisomers
(B) It can have a maximum of two stereoisomers
(C) It is a chiral compound
(D) It is an achiral compound
The given molecule is an achiral compound with a maximum of two stereoisomers, so options B and D are correct.
Structure and stereocenters
The structure in the question is a substituted hexane with two adjacent carbon atoms each bearing a methyl substituent and two hydrogens.
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Those two carbons are the only stereocenters (chiral centers) in the molecule.
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Therefore, the theoretical maximum number of stereoisomers is 2n=22=4, if there is no symmetry-related reduction.
However, because the two stereocenters are positioned symmetrically within the carbon chain and the substituents on both sides are identical, one of the possible configurations becomes a meso form, which is achiral despite having stereocenters.
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Thus, the actual stereoisomer set consists of:
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One pair of enantiomers
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One meso form (achiral)
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This reduces the observable stereoisomers to a maximum of two distinct configurational stereoisomers.
Option-wise explanation
Option (A): “It can have a maximum of four stereoisomers”
This statement considers only the formula 2n (where n=2 stereocenters) and assumes that all combinations give distinct stereoisomers.
Because a meso form (internally compensated, with a plane of symmetry) collapses two of the four configurations into the same achiral molecule, the actual number is reduced.
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Hence, Option (A) is incorrect.
Option (B): “It can have a maximum of two stereoisomers”
Due to the presence of an internal plane of symmetry, two of the four theoretical configurations represent the same meso compound, and the other two form one enantiomeric pair that is not distinguishable when the molecule is considered with its symmetry.
This leaves only two stereoisomers that can actually exist as distinct compounds under the given substitution pattern.
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Therefore, Option (B) is correct.
Option (C): “It is a chiral compound”
A molecule is chiral if it lacks any element of symmetry (such as a mirror plane or center of symmetry) and its mirror image is non-superimposable.
In this case, the molecule has an internal mirror plane passing through the central bond, and the substituents on both sides of the plane are identical, so the overall molecule is superimposable on its mirror image.
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Hence, Option (C) is incorrect.
Option (D): “It is an achiral compound”
Because of the internal plane of symmetry, the compound is a meso form overall and therefore achiral, despite containing stereocenters.
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Thus, Option (D) is correct.
SEO-friendly introduction
Understanding chirality and the actual number of stereoisomers in substituted hexanes is a common concept-tested area in IIT-JEE and other competitive exams. Correctly identifying chiral centers, recognizing meso forms, and applying the 2n rule with symmetry considerations are essential to solve such stereochemistry questions accurately.
